The purpose of this research is to investigate the nature of neural activity in pathways which transmit activity for slow and rapid eye movements between the visual and oculomotor systems. We postulate that one of the most important links between the visual and oculomotor systems lies in the mesencephalic reticular formation (MRF) and special emphasis will be placed on studies of this region. Alert trained monkeys will be used in this research. Their eye movements will be recorded by electro-oculography and by the scleral search coil technique. The MRF will be stimulated electrically to determine the locus of lowest threshold regions for inducing eye movements, and the induced deviations will be characterized. Electrolytic lesions will be made in the MRF to determine oculomotor deficits, and activity of single units will be recorded extracellulary to determine the neural code by which command information about eye movements is transmitted to the brain stem. Efferent activity from the oculomotor system to the visual system will also be studied in the MRF. Predictions of unit activity from control systems models of visual-oculomotor coupling will be tested and modified in accordance with our findings. These experiments will localize portions of the MRF which are involved in visual-oculomotor interaction. They should elucidate how the visual system controls the oculomotor system and provide information about the nature of efference feedback from the oculomotor to the visual system.